Evaluation of analgesic and sedative effects of repeated and increasing doses of xylazine HCl in sheep

The aim of the study was to investigate the sedative and analgesic biochemical and clinical effects of repeated and increasing doses of xylazine HCl in sheep. Five clinically healthy Akkaraman rams were used. Xylazine was administered intramuscularly at an initial dose of 0.4 mg/kg to induce sedation. The second, third and fourth doses were 20% larger than the previous dose, that is, 0.48, 0.57 and 0.68 mg/kg doses, respectively. They were administered intramuscularly four times at 4-day intervals. The rectal temperature, heart rate and respiratory rate, as well as the rumen motility of all animals, were evaluated before and after xylazine administration. The depths of sedation and analgesia and the control of reflexes, along with various biochemical parameters, were studied. Although the respiration rate increased until the 15th min, it approached the control value at the 30th min and decreased after the 45th min. Ruminal contractions progressively decreased from the 5th min to the 60th min. All levels of sedation were observed in all sheep. The degree of analgesic effect was 0 during mild and moderate sedation periods, and 1-2 during deep sedation. Of all biochemical parameters assessed, only the glucose concentration increased. It was therefore concluded that in order to obtain the same sedation level in sheep in the 4 days following an administration of xylazine, the previous dose should be increased by 20%.